Hot workable nickel base alloy



S. ABKOWITZ ETAL HOT WORKABLE NICKEL BASE ALLOY Get. 15', 1963 Filed April 7. 1961 Perce??? 47077;4//47/ 07 XM 771 5f/6J.: )fz/)vivre Oct. 15, 1963 Filed April 7, 1961 S. ABKOWITZ ETAL HOT WORKABLE NICKEL BASE ALLOY 3 Sheets-Sheet 2 I I I /,0

Oct. 15, 1963 Filed April 7, 1961 S. ABKOWITZ ETAL HOT WORKABLE NICKEL. BASE ALLOY 3 Sheets-Sheet 3 United States Patent O 3,107,i67 HOT WRKABLE NCKEL BASE ALLGY Stanley Ahkowitz and Robert A. Woodail, Utica, NX., assignors, by mesne assignments, to Special Metas, Inc., New Hartford, NX., a corporation o ieiaware Fied Apr. '7, 1961, Ser. No. 10,504 7 Ciaims. (Cl. 75-371) This invention relates to alloys adapted for high temperature use and particularly a high temperature nickel bearing alloy having improved hot working properties. Speciiically, these alloys are comprised essentially of nickel, cobalt, chromium, aluminum, molybdenum, and titanium with lesser amounts of elements selected from the group comprising tungsten, tantalum and columbium. Other elements may be present in trace amounts without significantly aecting the desirable characteristics of these alloys.

The present invention concerns alloys which might be considered to fall within the general ytype of alloys disclosed in Darmara U.S. Patent No. 2,809,110. Applicants alloys, however, by virtue of the novel compositions disclosed and claimed herein possess high temperature strength properties comparable to the commercial alloy based on the Darmara patent disclosure and further eX- hibit significantly improved hot workaoility characteristics.

The significant feature of the present invention is the discovery that when a relatively sml percent of tungsten (from about 0.1 to about 1.3 percent by weight) is included in an alloy containing selected `amounts of the above components, very desirable properties of hot workability inure to the alloy, particularly that of non-checking during hot rolling and cogging operations. Moreover, hot workability characteristics are attained without significant reduction in other alioy properties such as ultimate tensile strength, stress rupture at elevated temperatures and hardness. In addition, the present alloys therefore, iind particular utility in such structures as turbine blades, internal combustion engine valves, rotors, turbine discs, and air frame parts which are subjected to high temperatures but which must retain considerable strength during continuous use at these temperatures. in addition, these relatively small additions of tungsten do not significantly increase the density of the alloy which is important when the alloy is used in such high speed applications as turbine blades which generate very high centrifugal forces and exert considerable strain on the blades themselves and their supporting structure.

It has also been found that small amounts of tantalum and columbiuin or mixtures thereof may be used alone or jointly with tungsten to give improved hot workability properties to the alloy.

The present invention has as one of its principal objects'the formulation of an alloy comprising nickel, cobalt, chromium, aluminum, titanium and molybdenum having a relatively narrow and specific range of tungsten to impart improved hot workability properties to the alloy while retain'mg at least a minimum ultimate tensile strength of about 165 thousand lbs. per square inch (K si.) at room temperature and a rupture life of at least twenty-three hours at a temperature of about 1650 F. at 25 K s.i. continuous tension.

Another object is to impart to an alloy of the general .Patented 9ct. i5, 1963 composition comprising nickel, chromium, cobalt, and molybdenum, improved high temperature stress rupture characteristics by the addition thereto of controlled amounts of titanium and aluminum, and improved hot workability characteristics by the addition of controlled amounts of tungsten and/ or columbium and tantalum, wherein the tungsten and/or columbium and tantalum prevent the reduction in hot workability characteristics normally caused by the titanium and aluminum additions.

A further object is to provide an alloy comprising nickel, chromium, cobalt, titanium and aluminum with a relatively small and controlled amount of tungsten to impart to the alloy substantially reduced and equiaXed grain size in comparison to alloys of this nature which lack the tungsten.

A further general object is to provide a nickel base alloy of the above character possessing good optimum tensile strength, good rupture strength at elevated temperatures and hardness while also increasing high temperature workability characteristics over other nickel base alloys.

A further object is to provide a nickel, chromium, cobalt, molybdenum, aluminum and titanium alloy with specically limited ranges of elements selected from the group consisting of tungsten, tantalum and columbium and mixtures thereof to impart to the alloy desirable hot Workability, strength and density characteristics.

Other objects and advantages will be apparent from the following detailed description taken together with the accompanying drawings, wherein:

FlGURE l is a graph showing the stress rupture life of various test alloys;

FGURE 2 is a graph showing the eifect on hardness and workability of variations in titanium content of the alloy of the present invention; and

IGURE 3 is a photographic reproduction of bars produced from the diiferent test ingots.

As hereinabove indicated, the basic alloying constituents are nickel, chromium, cobalt, molybdenum, aluminum and titanium. rIlhe chromium may be present in amount between `about l5 to about 2l percent by weight, cobalt between about l0 lto about 14 percent, molybdenum about 4 to about 8 percent, aluminum about l to about 4 percent, and titanium from about l to about 4 percent. Elements from the group consisting of tungsten, tantalurn and columbium should be present from about 0.1 to about 1.3 percent, and the balance being substantially nickel with small allowances for impurities and processing aids such as carbon which acts as a deoxidizer. The best overall results have been attained through the use of tungsten alone of about one percent, but considerable uniqueness and utility is found in the alloys failing within the broader ranges specied above. These alloys are desirably produced by the vacuum induction melting process and all experimental ingots referred to herein were, in fact, melted in a vacuum furnace by induction heating.

The titanium and aluminum in the alloy of the present invention improves the strength of the material under high temperature use. The optimum percent of tungsten appears to be about l percent. As explained in detail below, experimental alloys of this tungsten content showed negligible corner checking and tearing under working conditions to which other test nickel base alloys were also subjected.

Table l below shows la comparison of three sets or heats of different composition ingots where the ingots within each heat had diierent amounts of titanium. The composition percentages in this table are accurate within normal weighing tolerances.

TABLE VI Heat No. 2-1095 Cb Ingots VC A1 Ti Mo Cr Co B W alud Ni No. 1 .05 2.0 1.0 6 O 19.0 12.0 0050 Bal No.3 .05 2.0 2.0 6 0 19.0 12.0 .0050 Bal. No.5 .05 2.0 3.0 19.0 12.0 .0050 Bal.

Heat No. 2-1096 No.1 .05 2.0 1.0 6.0 19.0 12.0 .0050 1.0 Bal. N0.3 .05 2.0 2.0 6.0 19.0 12.0 .0050 1.0 Bal. No.5 .05 2.0 3.0 6.0 19.0 12.0 .0050 1.0 Bal.

Heat No 2-1097 No.1 .05 2.0 1.0 6.0 19.0 12.0 .0050 1.0 Bal. No;3 .05 2.0 2.0 6.0 19.0 12.0 .0050 1.0. Bal. No.5 .05 2.0 3.0 6.0 19.0 12.0 .0050 1.0 Bal.

The working of the ingots in Table I proceeded in the following manner. All of the -ingots were of 9 lbs. weight and were originally substantially round. These ingots from heats 2-1095, 2-1096, and 2-l097 were charged into a furnace and raised to a temperature of 2140 F. The ingots were then removed from the furnace and were converted (cogged) to a 11A inch bar at starting temperalloys, only the bar from heat 2-1097 which contained the 1 percent tungsten addition showed practically a complete absence of corner checking or tearing. Moreover, as is shown in FIGURE No. l the average stress rupture life of the 2-1097 alloys was greater than the 2-1095 and 2-1096 alloys which indicates that the additional hot workability of ibc2-1097 alloys is obtained at no loss of strength and possibly a slight gain. FIGURE No. 1 further shows that an approximate linear relationship was obtained between titanium contents yand log rupture life for titanium contents in the'range of 1 to 3 percent.

it is noted that a recent experimental ingot of cornposition 4, Table 1V, was rolled (hot worked) into usable bar stock, and a careful evaluation was made of the weight of usable metal obtained from the ingot. This ingot was of sufficient size as to closely approximate production coiiditions and the recover] of usable metal was 16 percent better than that normally obtained by the Vassignee of the present invention in its production of the alloy identied as composition 3 in Table IV. Further, the recovery obtained with the present alloy composition 4 is comparable to that obtained in production of the Aalloy identified as composition 1 in Table IV, which may be seen (FIGURE l) to have much less desirable stress rupture properties.

Referring further to FIGURE No. 1, a comparison of stress rupture at l500 F. and 47 K s i. of approximately an average composition of heat number 2-1097V samples (composition 4 of Table IV below) was made with current wrought products numbered 1, 2, and 3 which have approximately the percentage by Weight compositions identied in Table IV below with small allowable amounts of impurities and additions such as iron, silicon, inanganese, sulfur and boron, the total of which does not exceed `about 4 to 5%.

atures of between 2ll0 and 2l30 E., and at iinishing TABLE IV temperatures of between 1790 and 1850" F. The bars were reheated twice during the coggmg operation. Table C A1 T M0 Cr Co W l Fe Nl II below shows the results 1n terms of checking.

TABLE H 1.2 3.0 4.2 19.5 13.5 0 Balance 2.0 3.15 1.5 10.5 7.5 8.5 9 5 Balance 3.o 3.o 4.0 17.5 16.5 0 Baiance Heat Na Ingot Result 2.o 3.o 6.o 19.0 12.0 i Balance 1 No checking. 3 45 The :one percent tungsten-3 percent titanium alloy here- 5 Checked ab0}1%"FPeP 0n come in was found superior on the basis of both strength and 1 Checked Worst. ol 9 nigots. 3 new W' comer checks, y hot workability and was found to compare weil with the 5 Checked approximately 4" deep on corners. e 1 Slight %checkmg on comers. current composition number 3 or Table IV. Table V 3 No checking. below shows this comparative data: 2-1097 5 Checked about 34" deep on corners. 50

TABLE IH Heat No Ingot Result 1 No checking. 3 Do. 5 Extensive checking. 1 Few small cheeks. 3 No checking.

' 5 Few small checks.

' 1 Do. 3 D0. 5 Do.

In FIGURE No. 3 photographs of the number 5 ing-ots of each heat are shown and the degree lof corner checking as set forth in Table Hl above is readily observable.

lt is particularly noted that of al1 the 3 percent titanium TABLE V Comparative Summary of Some Mechanical and Physical Properties of Compositions 3 and 4 of T ablel V Composi- Compotion 4 sition 3 Tensile properties at room temperature:

U.T.S, (K s.'.) IS7/198. 8 176 .02 T.Y.S. (K s.i 119. 5/117 110 .2 T.Y.S. (K si.) 128. 5/126.0 Elg. (pei'eeiit) 11. 2/18. et 10 RA. (percent) 12 9/18.4 16 Stress rupture, 1,5007 F., 47.5 K 5.1.

Rupture life (hrs.) 126.9/176 80-120 Elg. (percent) 15.7/21.9 23. 1/27. 0 Stress rupture, 1,050

Rupture life (hrs.) 45. 0/72. 7 45-145 l Elg. (percent) 16A/16.4 13.3 RA. (percent) 18. 0/17.7 9-25 As shown in FIGURE No. 2 the alloys show decreas- 4ing elongation and reduction in area with increasing titanium content in a manner which would appear to be normal and consistent with the increasing rupture life.

The effect of the three percent titanium and one percent tungsten on the nickel base alloy becomes readily apparma :All 0.5..

TABLE VI tungsten, and the balance being all nickel except for inconsequential amounts of impurities.

2. A highly workable nickel base alloy consisting of from about 18 to about 20 percent of chromium, from Results of Stress-Rupture Tests at 1,500 F., 47.5 K si. on

the 2-1095, 2-1096, and 2-1097 Alloys Percent Percent Percent Spec" en Rc. Rupt. life Percent Percent Ti W Cbrand No. hardness (hrs) elong. .A

1 0 2-1095-1a 27 11. 7 30. O 32. 9 1 0 2-1095-1b 10. 7 28. 6 40. 7 2 0 2-1095-3a 33 62. 0 33. 7 33. 1 2 0 2-1095-3b 42.0 31. 3 35. 5 3 0 2-1095-5a 37 134. 4 17. 5 23. 6 3 0 2-1095-5h 126. 5 15.9 19. 3 1 0 2-1096-12. 28 17. 0 44. 7 54. 1 1 0 2l0961b 16. 3 38. 0 55. 1 2 0 2-1096-3a 33 39. 2 20. 8 23. 2 3 0 24096-521. 39 103. 2 15. 4 1s. 3 3 0 2-1096-5b 129. 0 17. 7 18. 9 1 1 2-1097-12. 26 16. 9 26. 3 28. 1 l 1 2-1097--1b 18. 7 25. 9 31.3 2 l 2-l097-3a 34 54. 1 21. 6 38. 2 2 1 2-10973b 56. 2 16. 5 25. 2 3 1 2-1097-52. 40 126. 9 15. 7 23, 1 3 1 2-1097-5b 176 21. 9 27.0

It is particularly noted that the one percent substitutions of columbium and tantalum for the tungsten produces an alloy having desirable properties and utility though, not as pronounced as the one percent tungsten compositions.

In Table VII below are shown the physical characteristics of two samples #l and #2 having a 0.1 percent tungsten addition to the 3 percent titanium nickel base alloy.

TABLE VII This data indicates that these lower tungsten contents produce alloys having about 10,000 p.s.i. lower ultimate tensile strength at room temperature and about half the life under stress rupture conditions at 1500 F. as the 1 percent tungsten, 3 percent titanium alloy composition shown in Table l as ingot No. 5 of heat 2-1-097. The stress rupture strength of these lower tungsten alloys at 1650" F., however, approaches that of the 1 percent tungsten, 3 percent titanium alloys. Itis further apparent from Table VH that the low tungsten composition shows relatively good tensile strength properties. Further, the hot workability and subsequent recovery of the low tungsten composition was equivalent to that of the present alloy composition 4, Table IV. The evidence then appears to be substantial that relatively small amounts of tungsten when used with the 3 percent titanium compositions will eiectively produce doys of increased hot workability without substantially sacrificing tensile properties.

What is claimed is:

1. A highly workable nickel base alloy consisting of from about to about 20 percent of chromium, from about 10 to about 14 percent of cobalt, from about 5 to about 8 percent of molybdenum, from about 1 to about 4 percent of aluminum, from about 1 to about 4 percent of titanium, from about 0.1 to about 1.3 percent of about 11 to about 13 percent of cobalt, from about 5.5 to about 7.0 percent molybdenum, from about 1.9 to about 2.2 percent of aluminum, from about 2.9 to about 3.2 percent titanium, from about 0.9 to about 1.2 percent of tungsten, and the balance all nickel except for inconsequential amounts of impurities.

3. A highly workable nickel base alloy consisting of from about 17 to about 21 percent of chromium, from about 10 to about 14 percent of cobalt, from about 4 to about 8 percent of molybdenum, from about 1 to about 4 percent of aluminum, from `about 2 to about 4 percent of titanium, from about 0.1 to about 1.3 percent of tungsten, and the balance being all nickel except for inconsequential amounts of impurities.

4. A high heat workable alloy consisting of from about 15 to about 20 percent chromium, from about 10 to about 14 percent of cobalt, from about 5 to -about 8 percent of molybdenum, from about 1 to about 4 percent of aluminum, from about 1 to about 4 percent of titanium, from about 0.1 to about 1.3 percent of at least one alloying component selected from the group consisting of tungsten, tantalum, columbium and mixtures thereof, and the balance being all nickel except for inconsequential amounts of impurities.

5. A 'nigh heat workable alloy consisting of from about 15 to about 20 percent chromium, from about 10 to about 14 percent of cobalt, from about 5 to about 8 percent of molybdenum, from about 1 to about 4 percent of aluminum, from about 1 to about 4 percent of titanium, from about 0.1 to about 1.3 percent of at least one alloying component selected from the group consisting of tungsten, tantalum, columbium and mixtures thereof, and the balance being all nickel except for inconsequential amounts of impurities, said alloy being characterized by its ability to be hot worked and to withstand high stresses at elevated temperatures for extended periods of time without rupture.

6. A nickel base alloy consisting of from about 15 to about 20 percent of chromium, from about 10 to about 14 percent of cobalt, from about 5 to about 8 percent of molybdenum, from about 1 to about 4 percent of aluminum, from about 1 to about 4 percent of titanium, from about 0.1 to about 1.3 percent of tungsten and the balance being all nickel except for inconsequential amounts of impurities. l

7. A highly workable nickel base alloy consisting of from about 18 to about 2O percent of chromium, from about 11 to about 13 percent of cobalt, from about 5.5 to about 7.0 percent molybdenum, from about 1.0 to about References Cte in the file of this patent UNITED STATES PATENTS Darmara Oct. 8, 1957 Bounds et al May 27, 1958 Holl Aug. 1l, 1959 Bounds et al May 31, 1960 Bieber Mar. 28, 1961 Mami* n 

7. A HIGHLY WORKABLE NICKEL BASE ALLOY CONSISTING OF FROM ABOUT 18 TO ABOUT 20 PERCENT BY CHROMIUM, FROM ABOUT 11 TO ABOUT 13 PERCENT OF COBALT, FROM ABOUT 5.5 TO ABOUT 7.0 PERCENT MOLYBDENUM, FROM ABOUT 1.0 TO ABOUT 2.2 PERCENT OF ALUMINUM, FROM ABOUT 2.9 TO ABOUT 3.2 PERCENT OF TITANIUM, FROM ABOUT 0.9 TO ABOUT 1.2 PERCENT OF TUNGSTEN, AND THE BALANCE ALL NICKEL EXCEPT FOR INCONSEQUENTIAL AMOUNTS OF IMPURITIES, SAID ALLOY BEING CAPABLE OF WITHSTANDING AN APPLIED STRESS OF ABOUT TWENTY-FIVE THOUSAND POUNDS PER SQUARE INCH AT 1650*F. FOR A TIME IN EXCESS OF ABOUT 23 HOURS CONTINUOUSLY, WITHOUT RUPTURE. 